You have two purified samples of protein Y: the wild-type (nonmutated) protein and a mutant version with a single amino acid substitution. When washed through the same gel- filtration column, mutant protein Y runs through the column more slowly than the normal protein. Which of the following changes in the mutant protein is most likely to explain this result? (a) the loss of a binding site on the mutant-protein surface through which protein Y normally forms dimers (b) a change that results in the mutant protein acquiring an overall positive instead of a negative charge (c) a change that results in the mutant protein being larger than the wild-type protein (d) a change that results in the mutant protein having a slightly different shape from the wild-type protein

You have two purified samples of protein Y: the wild-type (nonmutated) protein and a mutant version with a single amino acid substitution. When washed through the same gel- filtration column, mutant protein Y runs through the column more slowly than the normal protein. Which of the following changes in the mutant protein is most likely to explain this result?

(a) the loss of a binding site on the mutant-protein surface through which protein Y normally forms dimers
(b) a change that results in the mutant protein acquiring an overall positive instead of a negative charge
(c) a change that results in the mutant protein being larger than the wild-type protein
(d) a change that results in the mutant protein having a slightly different shape from the wild-type protein

Which of the following globular proteins is used to form filaments as an intermediate step to assembly into hollow tubes?

Which of the following globular proteins is used to form filaments as an intermediate step to assembly into hollow tubes?

(a) tubulin
(b) actin
(c) keratin
(d) collagen

Globular proteins fold up into compact, spherical structures that have uneven surfaces. They tend to form multisubunit complexes, which also have a rounded shape. Fibrous proteins, in contrast, span relatively large distances within the cell and in the extracellular space. Which of the proteins below is not classified as a fibrous protein?

Globular proteins fold up into compact, spherical structures that have uneven surfaces. They tend to form multisubunit complexes, which also have a rounded shape. Fibrous proteins, in contrast, span relatively large distances within the cell and in the extracellular space. Which of the proteins below is not classified as a fibrous protein?

(a) elastase
(b) collagen
(c) keratin
(d) elastin

Protein structures have several different levels of organization. The primary structure of a protein is its amino acid sequence. The secondary and tertiary structures are more complicated. Consider the definitions below and select the one that best fits the term "protein domain."

Protein structures have several different levels of organization. The primary structure of a protein is its amino acid sequence. The secondary and tertiary structures are more complicated. Consider the definitions below and select the one that best fits the term "protein domain."

(a) a small cluster of a helices and ß sheets
(b) the tertiary structure of a substrate-binding pocket
(c) a complex of more than one polypeptide chain
(d) a protein segment that folds independently

ß Sheets can participate in the formation of amyloid fibers, which are insoluble protein aggregates. What drives the formation of amyloid fibers?

ß Sheets can participate in the formation of amyloid fibers, which are insoluble protein aggregates. What drives the formation of amyloid fibers?

(a) denaturation of proteins containing ß sheets
(b) extension of ß sheets into much longer ß strands
(c) formation of biofilms by infectious bacteria
(d) ß-sheet stabilization of abnormally folded proteins

Coiled-coils are typically found in proteins that require an elongated structural framework. Which of the following proteins do you expect to have a coiled-coil domain?

Coiled-coils are typically found in proteins that require an elongated structural framework. Which of the following proteins do you expect to have a coiled-coil domain?

(a) insulin
(b) collagen
(c) myoglobin
(d) porin

Two or three a helices can sometimes wrap around each other to form coiled-coils. The stable wrapping of one helix around another is typically driven by _____ interactions.

Two or three a helices can sometimes wrap around each other to form coiled-coils. The stable wrapping of one helix around another is typically driven by _____ interactions.

(a) hydrophilic
(b) hydrophobic
(c) van der Waals
(d) ionic